Electronic multichip packages have broad applications in fields such as personal and laptop computers. A popular multichip package is the dual inline memory module (DIMM) used for personal computer memory. The DIMM has a number of individual memory chips assembled on a rectangular printed circuit board (PCB), one example of what will be referred to here as a substrate. Input/output contacts are along one edge of the rectangular PCB. Such a package configuration is called a single-in-line package (SIP). For the SIP package, and generally any PCB or other substrate, electronic chips may be connected to both the front and back sides of the PCB. In particular, the DIMM typically has multiple memory chips connected to both sides of its PCB.
As the demand for smaller, more powerful computers continues, the density of electronic components increases. Electronic real estate is at a premium. Design features such as multilayer substrates have become commonplace to efficiently use substrate area. It is preferable to use all areas of a substrate such as a circuit board. It is generally not acceptable to design a circuit layout with unused areas. In addition, spacing of circuit features, such as integrated circuit chips, passive components, conductor traces, ground planes, and so on, becomes very dense, making conductor routing and general layout very challenging.